PDA compatible text scanner

ABSTRACT

An optical text scanning device compatible with a small handheld computer such as a personal digital assistant (PDA). The scanning device allows for a clear view of the text that is scanned simultaneous to the scanning process so that the operator can continuously align the device to the text. The scanned images of the text are converted in real-time to standard byte or word characters for subsequent display on the computer&#39;s viewing screen. The operator can quickly verify the accuracy of the conversion by comparing the displayed character with the actual character of text on the surface that is being scanned. Scanned text characters are stored in standard digital text files for ease of manipulation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part claiming priority to U.S.patent application Ser. No. 12/070,803 filed Feb. 21, 2008 now U.S. Pat.No. 8,056,805 which was a continuation-in-part claiming priority to U.S.patent application Ser. No. 11/156,814 filed Jun. 17, 2005, now U.S.Pat. No. 7,364,077.

TECHNICAL FIELD OF THE INVENTION

The invention relates to an optical text scanning device integrated witha small handheld computer such as a personal digital assistant (PDA). Inparticular, it teaches hardware and software concepts that allowsimultaneous optical viewing of the text as it is scanned and real-timeconversion of the scanned images to a standard text character stream forsubsequent display on a viewing screen.

BACKGROUND OF THE INVENTION

The small handheld computer or personal digital assistant (PDA) hasbecome a popular tool in the business world and more recently inpersonal communications. These devices have incorporated wirelessfunctions, cellular phone functions, personal audio, camera and videofunctions so that the market for such devices have expanded well beyondthe business person to the individual. The modern PDA operates as amultifunction device that many individuals carry with them at all times.

The PDA performs as a technology platform for the development of manynew value-added portable devices that can be integrated as hardware orsoftware add-ons to the PDA or linked through wireless functions. Thereis an ever growing market for PDA add-ons as the penetration of userscontinues to expand from business applications to personal applications.

A relevant class of PDA add-on devices has been developed to improve themeans of getting information into and out of the device. Cameras basedPDA add-ons are particularly effective because a large volume of data,typically 1 Megabyte to 10 Megabytes, can be collected optically andelectronically in a sub-second period of time. Closely related tooptical imaging is the field of optical scanning of documents. With theaddition of an optical scanner to a PDA, especially a PDA that haswireless or cellular capabilities, one can perform such tasks as, forexample, portable faxing of documents from the field, or, the scanningand uploading of a serial number from the field so that useful productinformation could be rapidly and accurately downloaded to a technicianduring a repair process.

With respect to the prior art, there are examples of optical scanningdevices that could be used in conjunction with a PDA. One example is anoptical wand. Optical wands are currently commercially available and maycommunicate with PDAs via an external cable, but these are notseamlessly integrated and require an extra hand-held device. Forexample, Faulkerson, U.S. Pat. No. 4,804,949 discloses a scanning devicein combination with a computer mouse connected via an umbilical cord toan external computer for OCR processing and text display. Faulkersondoes not teach the on-board integration of optical scanning functionsdirectly into a PDA.

Liao, U.S. Patent application No. 2004/0093444 A1 shows a PDA convertedinto an optical scanning device by adding an optical scanner assemblyonto the back surface. Liao also discloses the application of scanningbusiness card data into a PDA as bit-mapped images. Liao does notinclude a mechanism for illuminating the object to be scanned nor doeshe provide for simultaneous viewing of the object during the scan nordoes he provide a mechanism for real-time image conversion to digitalcharacters.

A similar disclosure is read in Huang, U.S. Patent Application No.2002/0169509 A1 in which the author discloses a handheld device, such asa PDA, capable of optical scanning. Huang discusses a feeder scannerdesign in which the PDA is situated inside a base housing and thedocuments are fed through a scanner channel via a set of rollers.Huang's design limits the scanned document sizes to those that can fitthrough the housing and otherwise suffers from similar limitations asLiao.

In Tsai, U.S. Patent Application No. 2003/0151780, a scanning device isdisclosed which includes a chassis for housing a PDA. Tsai alsodiscloses an optical sensing assembly engaged with the transmissionassembly so as to transfer the speed signal of the movement of thescanning device. Tsai's invention, while not limited by the documentsize, suffers from some of the same general limitations as the otherdesigns, namely that the viewing of the document is limited to abit-mapped image of the scanned input and that there is no immediateconversion to a standard digital character format. Real-time scanning oftext directly into standard byte or word character format would realizea significant improvement in portability over the prior art, since textfiles composed of standard digital characters have much smaller filesizes compared to image file formats.

SUMMARY OF THE INVENTION

The current invention is a PDA compatible text scanner with certainnovel features. The text scanner is incorporated into the PDA viaphysical, electronic, optical and software functions and can be used ina portable fashion as the combined unit is battery powered and handheldin size and weight. The text scanner can be a permanent fixture of thePDA or easily removable. The invention need not be limited to using aPDA platform: any type of portable handheld computer could besubstituted for the PDA, such as a handheld calculator, portable audioplayer or cell phone.

An objective of the invention is to allow text to be scanned easily froma variety of sources. The scanning function is not constrained to thesize or type of document. For example, but not by way of limitation, thedocument may be the size of a business card or the document may be partor all of the text in a large architectural scale blueprint. Theinvention does not constrain the geometry of the scanned text to a flatsurface but may be employed to scan text on curved surfaces such asmedicine containers or other product containers.

A feature of the preferred embodiment of this invention is that the textscanner assembly is constructed of optically transparent material anddesigned in such a way that the user can clearly view the text as it isscanned. The invention also incorporates a set of horizontal andvertical alignment marks that combine functionally with the clear viewof the scanned text allowing for ease of alignment and scanningaccuracy. The invention further discloses an illumination light guidethat not only eases the viewing of text, but also increases the signalto noise level of the electronic image capture and subsequent characterrecognition process. Another feature of the invention is that itconverts the scanned image of the text characters to standard byte orword digital character format in real time, for example to ASCII format,storing the digital character in memory and displaying the digitalcharacter on the PDA viewing screen. The invention incorporates the useof optical character recognition (OCR) processes in conjunction with thescan process.

The PDA compatible text scanner in the present invention utilizes knownelectronic interfaces found on PDAs such as a module expansion slot ormemory expansion slot (e.g. SecureDigital, MMC, compact flash, etc.).Modern PDAs may incorporate a built-in camera and light source. Thepreferred embodiment teaches a means of using camera devices that arebuilt-in to the PDA to accomplish the image acquisition. However,built-in PDA cameras are not a general requirement.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features and advantages,reference is now made to the detailed description along with theaccompanying figures in which corresponding numerals in the differentfigures refer to corresponding parts and in which:

FIG. 1 is a perspective drawing of one embodiment.

FIG. 2 (A, B) show two views of a preferred embodiment showing (A) thetop view, and (B) the bottom view.

FIG. 3 is a partial cross-sectional view of a preferred embodimentshowing the detail of a camera unit and optical assembly.

FIG. 4 (A-C) are drawings of a second embodiment showing views: (A) atop view, (B) a cross-sectional view AA showing the optical components,and (C) a bottom view.

FIG. 5 is block diagram of the electronic architecture.

FIG. 6 is a flow diagram.

FIG. 7(A-D) are drawings of a third embodiment showing views: (A) topview, (B) side view, (C) first cross-section view of an optical readerassembly attached to a PDA indicating the optical cavity and opticalcomponents, (D) second cross-section view of an optical reader assemblyattached to a PDA indicating the illuminator light guide.

FIG. 8(A-C) are drawings of a fourth embodiment showing views: (A) topview, (B) bottom view, (C) cross-section view of an optical readerassembly attached to a PDA indicating the optical cavity and opticalcomponents.

FIG. 9 is a drawing of a fifth embodiment showing a perspective view ofa rotatably attached optical reader assembly.

FIGS. 10A-10C are drawings of the fifth embodiment showing a side view,a non-rotated cross-section view and a rotated cross-section view of theoptical reader assembly and a mounting assembly.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 is shown a front perspective view of the preferred embodimentof a PDA text scanner device comprised of an optical reader assembly 200mechanically attached to a rectangular shaped PDA unit 100 by fourscrews 140 a, 140 b, 140 c and 140 d secured from the rear via holes 240a, 240 b, 240 c and 240 d. The top surface of reader assembly 200 isapproximately co-planar with and faces the same direction as the frontsurface of the PDA unit 100. Text print, printed figures or writtenobjects form an optical target 180 that lies on a surface 181 that isbeneath the bottom surface of optical reader assembly 200. The surface181 is located ideally from 0 to 2 cm below the bottom surface of theoptical reader assembly. The top and bottom surfaces of optical readerassembly 200 are approximately parallel. The optical reader assembly isfurther shown in FIG. 2.

Those familiar with PDA devices will realize that the mechanical meansby which the optical reader assembly attaches to the PDA unit isdependent upon the specific geometry of the PDA unit and that theinvention may easily encompass other means of attachment. For example,in other embodiments it may be beneficial to include a spring-loadedball-and-detent attachment mechanism (not shown) or a molded plasticform that releasably connects to the body of the PDA to allow for rapidand easy removal of the optical reader assembly when it is not in use orwhere access to certain features of the PDA (such as the camera) isrequired.

PDA unit 100 has a viewing screen 120 and control buttons 130 situatedon the front surface just below the viewing screen 120 and a built-incamera unit 151 on the rear surface. In use, scanned characters 185appear on the PDA viewing screen 120 as the optical target 180 isscanned into the device. An acquire button 220 is mounted on the topsurface of the optical reader assembly as shown along with an opticalreader indicator LED 225, also mounted on the optical reader assembly'stop surface.

Referring to FIG. 2, the optical reader assembly 200 includes an opticalblock 210 that is transparent and made of clear acrylic material 210 inthe preferred embodiment. Other materials such as glass or crystal canbe used in alternated embodiments. Colored transparent materials mayalso be used for special applications of the invention (such as in a lowlight embodiment or for aesthetic appeal such as in a children's toy).

The electrical connection between the optical reader assembly 200 andthe PDA unit 100 is accomplished using PDA electrical interface 150.Acquire button 220 and optical reader indicator LED 225 are connected byelectrical traces (not shown) to the electrical connector 250 whichmates with PDA electrical interface 150. In other embodiments, theoptical reader assembly 200 may incorporate the use of driverelectronics between the PDA electrical interface and said components toaccomplish electronic connections.

Continuing with FIGS. 2A and 2B, optical reader assembly 200incorporates alignment marks. In particular, there are a set ofhorizontal alignment marks 231 a and 231 b inscribed on the bottomsurface of optical reader assembly 200 and a vertical alignment mark 232inscribed on the top surface of the optical reader assembly 200.

Mirrors 270 a and 270 b and Lens 280 guide light from the bottom of theoptical reader assembly 200 to the back of the PDA unit 100. Furtherdetails of the optical components are disclosed in FIG. 3.

As shown in FIG. 3, a rhomboid shape optical cavity 252 is included inthe optical reader. The cavity forms a void in optical block 210 and isdefined by parallel surfaces 253 and 254, inner surface 255, outersurface 257 and lens mount 256. PDA camera unit 151 is typicallyrecessed into PDA unit 100 behind the PDA viewing screen 120. Mirror 270a is affixed with adhesive to surface 254 of the cavity with itsreflective surface facing optical target 180 at an angle of about 45degrees from the optical axis 274. Optical axis 274 is the axis definedby a line on which the centers of the optical components lie and isapproximately perpendicular to the back of the PDA as it exits opticalreader assembly 200. Mirror 270 b is adhered to surface 253 of thecavity with its reflective surface facing PDA camera unit 151 at anangle of about 45 degrees from optical axis 274. PDA camera unit 151incorporates a first optical lens 280, aperture stop 285 and opticalimage detector 290 as shown and it is built-in to the PDA unit 100. Thefirst optical lens 280 is positioned such that an optical image ofoptical target 180 is formed on the surface of optical image detector290. Aperture stop 285 serves to define the field of view and depth offield of the camera unit. In the preferred embodiment, optical readerassembly 200 incorporates a second optical lens 281 which is centered onoptical axis 274 and located just inside the bottom surface of opticalreader assembly 200 attached to lens mount 256. Mirrors 270 a and 270 bare fixed in such a way as to define optical ray paths 275 from thesurface of optical detector 290 to mirrors 270 to optical target 180thereby allowing optical target 180 to be imaged on optical detector290.

In the preferred embodiment the lenses are made of glass or plasticsubstrate and assembled as separate elements. In an alternateembodiment, at least one of the lenses may be molded as a part of theblock 210. In other embodiments, at least one of the optical lensfunctions may be combined with the mirror function by using a curvedmirror surface; the lens positions and overall magnification may vary aslong as the object is imaged onto the detector surface. The equationsfor determining lens position relative to the object and detector arewell known in the art.

In the preferred embodiment, the mirrors are front silvered flat glasssubstrates inserted into optical reader assembly 200 and fixed in placeby an adhesive. There are other means of accomplishing the function ofthe mirrors such as using multiple silvered substrates, silvering one ormore surfaces of the optical reader assembly 200 or inserting one ormore prisms into the optical cavity 252.

In the preferred embodiment, optical image detector 290 is acharge-coupled device (CCD) having approximately 500 by 500 pixels andlateral dimensions of one-half inch or less. The invention comprehendsthat other technology may be deployed in the PDA to accomplish theoptical to electronic conversion of the image—for example, a CMOSimaging device may be deployed in other embodiments. In the preferredembodiment, camera unit 151 is integral to the PDA unit 100 and mayaccomplish functions known in the art such as autofocus and zoom inconjunction with software resident on the host PDA. For example, theautofocus function will allow the optical target 180 to be placed atdifferent distances from the scanning unit. The resident software mayalso operate the integrated camera in a “black and white” mode wherebythe color information is discarded, thereby creating furtherefficiencies in the scanning process. Within the scope, it is envisionedthat the user can quickly remove the optical reader assembly so thatoptical images of text or other material could be taken in photographicmode and processed accordingly.

In an alternate embodiment shown in FIG. 4A, optical reader assembly 300is shown. The optical reader assembly 300 has optical body 310 made ofclear acrylic and has two mounting tabs 342 a and 342 b for mounting thedevice on the PDA unit. The mounting is accomplished by inserting themounting tabs into matching recesses into the PDA unit 100 and utilizingset screws to hold the mounting tabs 342 in place. Those familiar withPDA devices will realize that the mechanical means by which the opticalreader assembly attaches to the PDA unit is dependent upon the specificgeometry of the PDA unit and that the invention may easily encompassother means of attachment. For example, in other embodiments it may bebeneficial to include a spring-loaded ball-and-detent attachmentmechanism or a molded plastic form that snaps to the body of the PDA toallow for rapid and easy removal of the optical reader assembly when itis not in use.

Optical body 310 includes an acquire button 320, indicator LED 325attached to the top surface and an electrical connector 350 that mateswith PDA electrical interface 150 to connect said devices with PDA unit100.

Horizontal alignment marks 331 a, 331 b and vertical alignment mark 332are inscribed into the main body 310: the horizontal and vertical marksindicate the position of optical target 180 placement relative to themain body 310.

An optical cavity 352 is included in the optical body generally centeredat the horizontal midpoint marked by vertical alignment mark 332 asshown in FIG. 4A and FIG. 4C. Referring to FIG. 4B, optical cavity 352is defined by reflector support surface 353, inner surface 354, camerahousing 355, lens mount 356, illuminator light guide 360 and illuminatorhousing 358. The reflector support surface, inner surface, camerahousing, illuminator light guide and illuminator housing form a void inthe main body and comprise a housing for the optical components of thesystem. Mirror 370, in the preferred embodiment, is a front silveredpartially reflecting mirror of about 50% reflectivity attached by itsnon-reflective surface to reflector support surface 353 using anadhesive. The reflective surface of mirror 370 is facing optical target378 at an angle of about 45 degrees from the optical axis 374. Opticalaxis 374 is a line through the centers of the optical components and isapproximately perpendicular to the bottom face of the PDA unit as itexits optical reader assembly 300.

In other embodiments, mirror 370 may be replaced by a back silveredmirror or a triangular prism positioned to reflect light from opticaltarget 378 into the other optical components of the system. In otherembodiments, where the illuminator light guide is not directly behindthe mirror surface 353, the function of the mirror 370 can also beperformed by a reflective coating applied directly to reflector surface353.

Optical reader assembly 300 incorporates an optical lens 380 fixed tolens mount 356, aperture stop 385 which is fixed to and supported bycamera housing 355, and optical image detector 390 affixed to camerahousing 355. The optical lens 380 is centered on the optical axis 374and located just inside the bottom surface of optical reader assembly300; it is positioned approximately mid-way between the optical target378 and the optical detector 390 at about twice its focal distance fromoptical target 378 so that an image of optical target 378 is formed onthe surface of optical detector 390 with approximately unitmagnification. Aperture stop 385 serves to define the field of view anddepth of field. Optical ray paths 375 trace light from optical target378 to lens 380 to mirror 370 to optical detector 390, thereby allowingoptical target 378 to be imaged by optical detector 390. Optical lens380 may incorporate an anti-reflection coating to reduce stray lightreflections.

In the present embodiment the lens is made of glass or plastic substrateand assembled as a distinct element. In another embodiment, the lens maybe molded as a part of optical block 310. In other embodiments, theoptical lens function may be combined with the mirror function by usinga curved mirror surface; the lens position and overall magnification mayvary as long as the object is imaged onto the detector surface. Theequations for determining lens position relative to the object anddetector are well known in the art.

Optical reader assembly 300 has an illuminator light guide 360 which isa tapered hole situated just behind partially silvered mirror 370.Illuminator housing 358 is a hole connecting to illuminator light guide360 both of which are generally centered on the optical axis 374 asprojected through the mirror 370. Light source 340 is fixed insideilluminator housing 358 so that it protrudes into the illuminator lightguide 360 at approximately the rear focal plane of lens 380. Light fromlight source 340 propagates through the partially silvered mirror 370,through the lens 380 and exits optical reader assembly 300 approximatelycollimated to illuminate the optical target 378. Light source 340 istypically a light emitting diode (LED) chosen to match the spectralresponse of the optical detector 390, but other sources of illuminationare possible within the scope of the invention. Light source 340 ispowered by current received from PDA unit 100 via electrical interface150 and flexible wires (not shown) which interconnect to electricalconnector 350. Electrical connector 350 provides a mating interface withPDA electrical interface 150.

In alternate embodiments of the invention the illumination guide isaccomplished by the insertion of one or more optical waveguides such asa void in the optical block or optical fibers. The illuminator lightspectrum and optical waveguide may be chosen to match the wavelengthpeak sensitivity of the optical detector, such as in the infrared rangeso as to illuminate a large area of text in the vicinity of the opticalreader. The illumination light spectrum may also be chosen in thevisible spectrum to enhance the user's ability to see the material to bescanned, especially in the absence of ambient light. In such embodimentswhere an optical waveguide is deployed, the partially silvered mirrormay be replaced by a fully reflecting mirror or prism.

Optical image detector 390 is a charge-coupled device (CCD) havingapproximately 500 by 500 pixels and lateral dimensions of one-half inchor less. Optical detector 390 can be model TC237 680×500 pixelmonochrome CCD made by Texas Instruments of Dallas, Tex. The inventioncomprehends that other technology may be used to accomplish the opticalto electronic conversion of the image—for example, a CMOS imaging devicemay be deployed in other embodiments. The camera may accomplishfunctions known in the art such as autofocus and zoom in conjunctionwith software resident on the host PDA. For example, the autofocusfunction will allow the optical target 378 to be placed at differentdistances from the optical reader assembly. The resident software mayalso operate the integrated camera in a “black and white” mode wherebythe color information is discarded, thereby creating furtherefficiencies in the scanning process. Within the scope, it is envisionedthat the user can easily remove the optical reader assembly so thatoptical images of text or other material could be taken in photographicmode and processed accordingly.

Optical detector 390 is physically connected to control circuit board395. Control circuit board 395 provides on-board memory, clocking,electrical buffering and computer interface functions. Control circuitboard 395 is electronically connected to the PDA unit 100 via flexiblecabling (not shown) which interconnects to electrical connector 350which mates with PDA electrical interface 150.

Optical reader assembly 300 may incorporate the use of other driverelectronics (not shown) between the PDA electrical interface 150, lightsource 340, acquire button 320 or indicator LED 325 to accomplishelectronic connection.

In a third embodiment shown in FIGS. 7A-7D, optical reader assembly 700is shown. The optical reader assembly 700 includes optical body 710 madeof clear acrylic and has two mounting tabs 742 a and 742 b for mountingthe device on PDA unit. The mounting is accomplished by inserting themounting tabs into matching recesses into PDA unit 100 and utilizing setscrews to hold mounting tabs 742 a and 742 b in place. Those familiarwith PDA devices will realize that the mechanical means by which theoptical reader assembly attaches to the PDA unit is dependent upon thespecific geometry of the PDA unit and that the invention may easilyencompass other means of attachment. For example, in other embodimentsit may be beneficial to include a spring-loaded ball-and-detentattachment mechanism or a molded plastic form that snaps to the body ofthe PDA to allow for rapid and easy removal of the optical readerassembly when it is not in use.

Optical reader assembly 700 includes an optical body made of clearacrylic material 710, an acquire button 720, indicator LED 725 attachedto the top surface and an electrical connector 750 that mates with PDAelectrical interface 150 to connect said devices with the PDA unit 100.

Horizontal alignment marks 731 a, 731 b and vertical alignment mark 732are inscribed into the optical body 710: the horizontal and verticalmarks indicate the position of optical target 180 placement relative tothe optical body 710.

Optical cavity 752 is included in optical body 710 and centered atgenerally the horizontal midpoint marked by vertical alignment mark 732as shown in FIG. 7A. Referring to FIG. 7C, the optical cavity 752 isdefined by reflector support surface 753, inner surface 754 and lensmount 756. The reflector support surface and inner surface form a voidin the main body and comprise a housing 755 for the optical componentsof the system. Mirror 770, in the present embodiment, is a frontsilvered mirror of high reflectivity attached by its non-reflectivesurface to reflector support surface 753. The reflective surface ofmirror 770 faces optical target 180 at an angle of about 45 degrees fromthe optical axis 774 which is a line generally through the centers ofthe optical components and is approximately perpendicular to the bottomface of the PDA unit as it exits the optical reader assembly 700.

In other embodiments, mirror 770 may be replaced by a back silveredmirror or a triangular prism positioned to reflect light from theoptical target 180 into the other optical components of the system. Inother embodiments, the function of the mirror 770 can also be performedby a reflective coating applied directly to reflector surface 753.

Optical reader assembly 700 incorporates a primary optical lens 780fixed to lens mount 756. The primary optical lens 780 is centered on theoptical axis 774 and located just inside the bottom surface of opticalreader assembly 700.

Continuing with FIG. 7C and FIG. 1, PDA camera unit 151 faces thevertical and is recessed into the PDA unit 100 at the upper end of thePDA. PDA camera unit 151 incorporates a camera lens 781, aperture stop785 and optical image detector 790 mounted to support 755 as shown.Primary optical lens 780 is positioned approximately its focal distanceaway from optical target 180 such that optical rays 775 are renderednearly parallel as they enter PDA camera unit 151 resulting in anoptical image of optical target 180 on the surface of optical imagedetector 790. The aperture stop 785 serves to define the field of viewand depth of field of the camera unit.

In the third embodiment, lens 180 is made of glass or plastic substrateand assembled as a distinct element. In an alternate embodiment, thelens may be molded as a part of optical block 710. In other embodiments,the optical lens function may be combined with the mirror function byusing a curved mirror surface; the lens position and overallmagnification may vary as long as the object is imaged onto the detectorsurface. The equations for determining lens position relative to theobject and detector are well known in the art.

Also in the third embodiment, the mirror is a front silvered flat glasssubstrate inserted into optical reader assembly 700 and fixed in placeby an adhesive. There are other means of accomplishing the function ofthe mirrors such as using multiple silvered substrates, silvering one ormore surfaces of optical reader assembly 700 or inserting one or moreprisms into optical cavity 752.

In the third embodiment, optical image detector 790 is a charge-coupleddevice (CCD) having approximately 500 by 500 pixels and lateraldimensions of one-half inch or less. The invention comprehends thatother technology may be used to accomplish the optical to electronicconversion of the image—for example, a CMOS imaging device may bedeployed. The camera unit 151 is integral to the PDA unit 100 and mayaccomplish functions known in the art such as autofocus and zoom inconjunction with software resident on the host PDA. For example, theautofocus function will allow the optical target 180 to be placed atdifferent distances from the scanning unit. The resident software mayalso allow the integrated camera to operate in a “black and white” modewhereby the color information is discarded, thereby creating furtherefficiencies in the scanning process. Within the scope, it is envisionedthat the user can easily remove the optical reader assembly so thatoptical images of text or other material could be taken in photographicmode and processed accordingly.

As shown in FIG. 7D, optical reader assembly 700 has an illuminatorlight guide 760 which is a hole in optical block 710 from the interfacesurface 744 to the bottom surface 743. FIGS. 7A and 7B show top and sideviews of the illuminator light guide 760. A light source 740 with itcollimating lens 741 is a part of the PDA unit 100. The position andangle of the illuminator light guide 760 is made to match the positionsof the collimating lens 741 and optical target position 180. Light fromlight source 740 propagates through the illuminator light guide 760along optical rays 776 and exits the optical reader assembly 700 toilluminate the optical target 180.

Other embodiments of the invention are conceived in which theillumination light guide is accomplished using different shaped voidsthan the present embodiment or optical fibers inserted into the opticalblock 710. The illuminator light spectrum and optical waveguide may alsobe chosen so as to illuminate a large area of text in the vicinity ofthe optical reader to enhance the user's ability to see the material tobe scanned, especially in the absence of ambient light. The illuminationlight spectrum may also be chosen to match the peak sensitivity of theoptical detector.

In a fourth embodiment shown in FIG. 8, optical reader assembly 800 isshown. The optical reader assembly 800 is made of clear acrylic and hastwo mounting tabs 842 a and 842 b for mounting the device on PDA unit100. The mounting is accomplished by inserting the mounting tabs intomatching recesses into PDA unit 100 and utilizing set screws to holdmounting tabs 842 in place. Those familiar with PDA devices will realizethat the mechanical means by which the optical reader assembly attachesto the PDA unit is dependent upon the specific geometry of the PDA unitand that the invention may easily encompass other means of attachment.For example, in other embodiments it may be beneficial to include aspring-loaded ball-and-detent attachment mechanism or a molded plasticform that snaps to the body of the PDA to allow for rapid and easyremoval of the optical reader assembly when it is not in use.

Optical reader assembly 800 includes an optical body made of clearacrylic material 810, an acquire button 820, indicator LED 825 attachedto the top surface and an electrical connector 850 that mates with PDAelectrical interface 151 to connect said devices with PDA unit 100.

Horizontal alignment marks 831 a, 831 b and vertical alignment mark 832are inscribed into optical body 810: the horizontal and vertical marksindicate the position of optical target 180 placement relative to theoptical body 810.

A cylindrical optical cavity 852 is included in optical body 810 andgenerally centered at the horizontal midpoint marked by verticalalignment mark 832 as shown in FIG. 8A and FIG. 8B. Referring to FIG.8C, optical cavity 852 includes a threaded inner surface 854 and bottomopening 886 forming a void in the optical body and comprising a housingfor the optical components of the system. The optical components aremounted and threaded into the cylindrical optical cavity 852 in innersurface 854 and held in place by adhesive. Optical axis 874 is a linegenerally through the centers of the optical components and isapproximately perpendicular to the PDA unit as it exits optical readerassembly 800.

Reader assembly 800 incorporates an optical lens 880 fixed to lens mount856 which is threaded into optical cavity 852. Aperture stop 885 isfixed to and supported by optical cavity 852. Optical image detector 890is affixed to camera electronics 895 which abuts electronics mount 897and is held in place by cap 896 threaded into the top of optical cavity852. Optical lens 880 is positioned approximately mid-way betweenoptical target 180 and optical detector 890 at about twice its focaldistance from optical target 180 so that an image of optical target 180is formed on the surface of optical detector 890 with approximately unitmagnification. Aperture stop 885 serves to define the field of view anddepth of field. Optical ray paths 875 trace light from optical target180 to lens 880 to optical detector 890, thereby allowing optical target180 to be imaged by optical detector 890. Optical lens 880 mayincorporate an anti-reflection coating to reduce stray lightreflections.

In the present embodiment the lens is made of glass or plastic substrateand assembled as a separate element. In another embodiment, the lens maybe molded as a part of optical block 810. The equations for determininglens position relative to the object and detector are well known in theart.

Optical image detector 890 is a charge-coupled device (CCD) havingapproximately 500 by 500 pixels and lateral dimensions of one-half inchor less. The invention comprehends that other technology may be used toaccomplish the optical to electronic conversion of the image—forexample, a CMOS imaging device may be deployed in other embodiments. Thecamera may accomplish functions known in the art such as autofocus andzoom in conjunction with software resident on the host PDA. For example,the autofocus function will allow optical target 180 to be placed atdifferent distances from the optical reader assembly. The residentsoftware may also operate the integrated camera in a “black and white”mode whereby the color information is discarded, thereby creatingfurther efficiencies in the scanning process.

Optical detector 890 is physically and electrically connected to cameraelectronics 895. Camera electronics 895 provides on-board memory,clocking, electrical buffering and computer interface functions. Cameraelectronics 895 is electronically connected to PDA unit 100 via cabling892 which interconnects to the electrical connector 850 which mates withPDA electrical interface 150.

Optical reader assembly 800 may incorporate the use of other driverelectronics (not shown) between PDA electrical interface 150, acquirebutton 820 or indicator LED 825 to accomplish electronic connection.

In a fifth embodiment shown in FIGS. 9 and 10A-10C, optical readerassembly 800 is rotatably attached to PDA unit 100 by a hinge 905attached to the optical reader assembly and a mounting assembly 906.Mounting assembly 906 includes a frame and a cavity 908. Mountingassembly 906 is attached to PDA unit 100 by a releasable friction fitbetween cavity 907 and PDA Unit 100. Optical reader assembly 800 iselectrically connected to flexible connector 910. Flexible connector 910is electrically connected to connector 850. Connector 850 is, in turn,connected to the PDA. Optical reader assembly 800 includes a pocket 930to store excess flexible connector material.

In use, hinge 905 enables the PDA to be held at a different angle thanthe optical reader assembly. The angle allows a more comfortable andnatural angle for scanning lengthy text subjects and thereforeaccommodates the user.

The electronic architecture of the invention is shown in FIG. 5. PDAunit 100 includes a microprocessor 110 and electronic memory 115.Certain software programs may be stored in memory 115 and executed bymicroprocessor 110 to operate on PDA unit 100 to accomplish tasks thatwill be described. The type of microprocessor 110 and the storagecapability of the electronic memory 115 are not critical to theinvention except that they should be chosen to efficiently accomplishthe tasks that will be described. For example, in another embodiment,microprocessor 110 may be composed of two processors, one processordedicated to the user interface and normal functioning of the PDA; theother processor dedicated to image and OCR processing. Either or bothprocessors could be a RISC class processor.

Microprocessor 110 accepts user stimulus electronically from the acquirebutton 220 and PDA buttons 130 to control the scanning process. As theoptical target 180 is scanned, microprocessor 110 displays textcharacters 185 on PDA viewing screen 120. During the scan process,certain states and conditions of the process may be indicated by PDAviewing screen 120 or the indicator LED 225. In the alternateembodiments, the acquire buttons and indicator LEDs interact with themicroprocessor in a similar way to the preferred embodiment.

To scan text, PDA camera unit 151 acquires an electronic image 155 of acharacter of text in optical target 180. The electronic image 155 is abit-mapped pixilated representation of the optical image that exists onthe surface of optical detector 290 and would typically contain 500 by500 bytes i.e. 250 kbytes total. That image is stored momentarily in theon-board memory of camera unit 151 until the PDA microprocessor 110extracts the electronic image 155 from the camera unit 151 and stores itin electronic memory 115.

Microprocessor 110 then acts on the electronic image 155 stored inmemory 115 to convert the electronic image 155 into a byte or worddigital character representation, such as the ASCII representation. Thebyte or word representing the digital character, which in turnrepresents the character of text in optical target 180 that was scanned,is then stored into an available location in memory 115. The portion ofmemory 115 that holds the electronic image 155 is then freed to be usedfor the next character in the scan.

FIG. 6 is a flow chart of a scan process that accomplishes the overalltext scanning task. The process begins with step 501 when a textscanning application software program 500 residing in the electronicmemory 115 of the PDA unit 100 is initiated. Once the program starts, itperforms the step 505 of activating the acquire button 220 and cameraunit 151, then step 508 of verifying the electronic integrity of theoptical reader assembly 200 and lighting indicator 225, therebysignaling the operator that the PDA unit 100 is ready to scan text. Uponready signal, step 510 is performed where the optical reader assembly200 is placed over optical target 180 and aligned with alignment marks231 and 232. After alignment the software program 500 waits to takefurther action until the acquire button is pressed in step 512. Whenacquire button 220 is pressed down, the software program 500 leaves step512 and moves to step 513 in which it sets scanning state to “ON”. Insubsequent step 516, the electronic image data 155 is acquired fromcamera unit 151 and this image represents the current character situatedin the optical path 275. Microprocessor 110 processes the electronicdata 155 utilizing optical character recognition (OCR) software code instep 519. If the OCR process is successful, a valid byte or word digitalcharacter within the available character set will be selected and instep 522 the OCR process will return a valid character to themicroprocessor 110 signaling that it was successful. If the OCR processis unable to match a valid character, it will return a flag to themicroprocessor 110 indicating failure. OCR algorithms are well known inthe art such that commercially available software code may be utilizedto accomplish this task.

If OCR step 522 indicates success, then software program 500 proceeds tostep 525 in which microprocessor 110 stores the character in memory 115and on to step 526 in which the microprocessor 110 displays thecharacter on the PDA viewing screen 120. Moving to step 528 then, themicroprocessor 110 checks the state of the acquire button 220: if thebutton is still pressed down, then the software program 500 flows backto step 516 to repeat. If acquire button 220 is released, then thescanning state is changed to “OFF” in step 550 and the operator isqueried in step 555 to scan again or to stop. If the operator selects tocontinue scanning, the scanning process is repeated beginning with step510. If the operator selects to stop scanning then the process moves tostep 560. In step 560 and subsequent steps 563 and 565, the scanned andprocessed text is edited if the operator chooses to, is saved to a textfile and the program exits, respectively.

If OCR step 522 indicates failure, then the scan process proceedsimmediately to step 545 in which the microprocessor 110 displays anerror condition on the PDA viewing screen 120 indicating to the operatorthat the last character was not valid and that the operator must rescan.The software program proceeds to check that the acquire button is stilldepressed in step 528. If the button is depressed, then the deviceacquires a new image and the conversion process repeats. If the acquirebutton is released, the scanning state is switched to “OFF” in step 550and the scan process moves to step 555 to query the user to continuescanning or not. The software program 500 proceeds as described beforefrom that point. In other embodiments, the PDA may signal the operatorwith the indicator LED 225 or with audio sounds instead of or in concertwith the visual signals on the PDA viewing screen.

In another embodiment of the invention, the scan process is altered byinserting a step between step 516 and step 519. The new software stepdeconvolves and transforms the electronic image data 155 using the knowntransfer function for the optical components so as to remove thedistortion effects of optical aberrations.

While this invention has been described in reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the appended claims encompassany such modifications or embodiments.

The invention claimed is:
 1. A PDA scanner for a PDA with amicroprocessor, a PDA memory and a PDA display, comprising: an opticalreader assembly, pivotally attached to the PDA, comprising a cameraelement and an optical control element wherein the optical controlelement is in an optical path between a subject to be scanned and thecamera element; the optical reader assembly configured to electricallycapture an image of the subject to be scanned and to electricallytransfer the image to the PDA; wherein the optical control elementcomprises a light directing channel in the optical reader assemblybetween the camera element and the subject to be scanned; and, whereinthe light directing channel is an optical fiber.